Brief

Metal filters are meant to replace paper, but few of them brew like it. Most are perforated all the way to the rim. Water finds the easiest path, runs through the upper holes and down the sides, and never passes through the coffee. Many also use large holes, so the water drains too fast and the cup comes out thin.

Design

The upper part of the filter has no holes. Water can only leave through the coffee bed, so none of it bypasses the grounds.

Below that band, a calibrated hole pattern with a fine mesh inside sets the flow. It was tuned to match the flow rate of Hario paper filters, so the brew time and body are close to what a paper filter gives. The difference is that the filter is used again and again.